When working the earth, especially at planting time, it is not uncommon for a farmer to connect together various implements, one after the other, in a "train" of implements. For example, at the head of a train would be the tractor, which in turn could be followed by a seeder trailer carrying a pneumatic seed distributor, the trailer towing a cultivator carrying cultivator shanks and pneumatic seed drills, and the cultivator towing a fertilizer applicator or spreader. Needless to say, any number of implements could make up the train, the foregoing being but one suggestion.
In the past, implements in a train have been simply connected together with little or no regard to the effects of the hitching systems used. This has led to the trains being very long and, therefore, being very cumbersome. The operator of the train would have difficulty in viewing and appreciating the action of the rearmost units of the train. Also, problems exist in making short-radius turns since long hitch systems tend to increase the turning circle diameter of a train of implements. Furthermore, long hitch systems make it difficult for a towed unit to follow the undulations in the ground uniformly and, in the case of a cultivator, there is thus difficulty in maintaining a uniform working depth. Problems in maintaining a uniform working depth are compounded by the lever action of a long hitch system over rolling terrain. One other problem of long hitch systems results from the vertical load transferred from the ground working implement, such as the cultivator, to the intermediate unit(s). The increase in vertical load on the intermediate unit(s) is transferred to the wheels and supports of such intermediate unit(s) and the obvious result is increased wear thereof.
There have been several attempts at improving hitching systems, as for example by providing means for varying the vertical height of implements towed by a tractor (Canadian Pat. No. 707,124 of Apr. 6, 1965 to Albert M. Jongeneel); by providing means for adapting one type of hitch system to another type of system (Canadian Pat. No. 878,248 of Aug. 17, 1971 to Massey-Ferguson, Inc.); and by varying the horizontal levelling relationship between implements in a train of implements (Canadian Pat. No. 1,104,427 of July 7, 1981 to Prasco Super Seeder Ltd.). None of these patents discloses a hitching system which overcomes the problems enumerated above.